Obtaining high-resolution structural and molecular information from intact brain tissue is a key goal, but existing techniques face several limitations. In a new approach, named CLARITY by the authors, an intact mouse brain tissue was hybridized with a hydrogel to preserve its structure and then stripped of lipids. The resulting sample was optically transparent and could be penetrated by a range of chemical and biological reagents, enabling the authors to visualize many structural and molecular features of the intact brain.